1. Field of the Invention
The invention relates to a reader for data interchange with a mobile data memory.
2. Description of the Related Art
In industrial applications, but also in other areas, goods and capital goods are identified by using mobile data memories which are sensed and read wirelessly by an electromagnetic field. This relates particularly to Ultra High Frequency (UHF) RFID transponders, which are in widespread use for the cited purposes. Particularly in industry (production) and in automotive construction, much higher reading rates are required in comparison with other fields of use, for example, materials management, retail and logistics, where the reading rate gives the proportion of successful access operations on the data memories. This is typically approximately 99.98% in the processing industry and in automotive construction.
Precisely in the industrial environment, in which the particularly good reading rates are required, data interchange with the data memories (transponders) is frequently made more difficult by external conditions, for example, the presence of metallic, reflective surfaces or electromagnetic interference, movements by the articles denoted by the data memories. So as nevertheless to be able to achieve the high reading rates that are required, it is absolutely essential to be able to perform precise analysis in the event of faults. Only in this way is it possible to identify and remedy causes of the faults.
Usually, relatively frequent faults, i.e., read errors, involve the use of measurement receivers in proximity to the reader used, where the measurement receivers are used to record and later evaluate the data interchange between a reader and the sensed data memories (transponders). This means that all the activity on the “air interface” of the radio channels used is recorded (“logged”), after which the recorded profile of the high frequency signal or intermediate frequency signal is immediately (“online”) or later (“offline”) searched for a cause of the fault, such as interference frequencies, field attenuations, protocol errors or signal overlaps (overlap, echoes).
To date, the measurement receivers used for error analysis are what are known as “RealTime Spectrum Analyser” (RSA). To this end, a measurement antenna that is used to supply the high frequency signals to the RSA is placed directly next to the reading position, i.e., the site of the productively used reader or the antenna thereof. The signal is continuously recorded and stored. In the event of an error, the recording is stopped (manually or automatically by a controller to which the reader is connected), and the error is analyzed.
This approach to fault analysis has disadvantages, however. By way of example, it is very sophisticated to obtain and place a specific measurement receiver following identification of an increased error rate, where the antenna of the measurement receiver needs to be arranged as close as possible beside the antenna of the productively used reader. Besides the sophistication associated therewith, it must be expected that the antenna of the measurement receiver in turn influences the measured electromagnetic field, which means that the presence of the antenna of the measurement receiver corrupts the measurement result. Furthermore, although the measurement receiver can be used to comprehend what is happening “on the air interface”, it can only indirectly explain which signal has actually been received and processed by the productive reader. Furthermore, it is difficult in the case of such an analysis for individual erroneous read operations to be associated with particular sections of the material recorded for analysis purposes, this generally requiring precise synchronization between the measurement receiver and the productive reader. A further disadvantage is that the method described, i.e., the use of a specific measurement receiver in such arrangements as have a greater than average number of errors, cannot be used at all to analyze the errors that occurred originally, but instead it must be relied upon that the errors occur again with the same cause as soon as the measurement receiver is used.